Color television



NOV. 14, 1950 T, w, CHEW 2,529,485

' COLOR TELEVISION Filed'Oct. 9, 1945 'k Sheets-Sheet 1 SYNCHRONIZING'SIGNAL COMMUTED CURRENT SOURCE (O l I 3)wc-n OL THORNTON W. CHEW Nov;14, 1950 Filed Oct. 9, 1945 T. w. CHEW COLOR mumsron 7 Sheets-Sheet 2THORNTON w. CHEW Nov. 14, 1950 T. w. CHEW 2,529,435

COLOR TELEVISION Filed 001.3 9, 1945 '1 Sheets-Sheet 3 CD G) 60 Nov. 11950 Filed Oct. 9, 1945 W. CHE

COLOR TELEVISION 7 s ts-Sheet 4 I I/ I I VIDEO AMPLIFIER TER PRIMARY ANDCOMMUTATOR 39 RAS 57 DEFLEGTION (SECONDARY clRcu'Ts A DEFLECTION) aRomzmG I PULSE SEPARATION 4| CIRCUITS R.E TUNER AND AMPLIFIER AmpDEMODULATO Nov. 14, 1950 T. w. CHEW 2,529,485

' COLOR TELEVISION Filed 001'.- 9, 1945 v 7 Sheets-Sheet 6 ELECTRICCURRENT SOURCE OF COMMUTED THORNTON W. CHEW Nov. 14, 1950 T. w. CHEW2,52

COLOR TELEVISION Filed Oct. 9, 1945 7 Sheets-Sheet 7 grwc/wtom THORNTONW. CHEW Patented Nov. 14, 1950 UNITED STATES PATENT OFFICE COLORTELEVISION Thornton W. Chew, United States Navy Application October 9,1945, Serial No. 621,397

33 Claims. (Cl. 178-53) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) This invention relates totelevision systems and more particularly to methods of and means forproducing television images in their natural color or in perspective.

In .one method of natural color television, images are transmitted byforming partial images of the object seen in terms of each of theprimary colors (red, green, and blue), and then super imposing thesepartial images at the.receiver to form a composite image in naturalcolor. In one receiving system, for use with this method, the partialimages are'selected by mechanically alternating a group 01' colorfilters intercepting the optical path to the cathode ray tube screen.This mechanical method requires high speed moving.

parts with consequent noise, vibration, and wear. The color filters mustbe relatively large and comolicate cabinet design. Furthermore, thelight )8? in the filters reduces the intensity of the usable image andsynchronization with the translmitter is more difilcult than 'in anelectronic system.

In another receiving system which avoids the use of mechanicallyalternated color filters..the partial images corresponding to theseparate colors are'displayed on separate interleaved and superposedluminescent surfaces each surface being excited to one of the threeprimary colors by a separate electron beam. The requirement of separatescanning beams creates a serious problem of obtaining and maintainingthree rasters of identical size, position and shape, and of providingcompensation for keystoning resulting from the nonperpendicularity ofthe beam to the plane of the screen. Furthermore, three separatescanning systems are required.

It has been proposed to employ a picture screen having a plurality ofextremely narrow adjacent strips of fluorescent material with everythird strip adapted to produce light of one of the three primary colors.This may be accomplished by use of filters or by use of three phosphorseach producing one of the three primary colors directly. The screenelements are made so small compared to one image element that any imageelement may appear to be presented in any one of the three primarycolors. or any combination of these three colors. A singleimage-modulated electron beam successively scans each separate colorgroup of elements in synchronism with the transmitter. The partialimages presented by'the three color groups of elements are then added bypersistence of vision of the human eye to form a composite natural colorimage.

The above mentioned method of color television requires a very fine andprecise adjustment in the 2 deflection oi the image display orpresentation tube electron beam because the individual strips orelements must be of extremely small width in order that they not bediscernible from another by the unaided human eye at a useful viewingdistance from the screen. Heretoiore, it has been impossible to adjustthe scanning of the image display or presentation tube electron beam toaccomplish this precise adjustment. This is not only the result ofdifilcuity in achieving the necessary exact control of the deflectingfields but also is caused by small external influences such as theearth's magnetic field, stray electric fields, etc. These influences.acting early in the beam path can cause a significant error at thescreen where precise adjustment is required.

In Patent 2,307,188, it is proposed to accomplish the necessary exactcontrol of the electron beam by applying an. electric potential ofproper polarity between the various screen elements so that theelectrons will be urged toward the desired color element. That is, arelatively positive and static electric charge which attracts thenegative electrons is applied to the particular color element it isdesired to excite to luminescence. This requires high potential betweenthe adjacent screen elements to achieve the necessary control over theelectron stream. The requirement of resolution of image details demandsthat each screen element be spaced from the other, center to center, adistance less than the dimension of one image element. This smallspacing will not permit these high voltage difierences between elementssince arcs will occur and the screen will be damaged. Furthermore, thesehigh voltages are most economically supplied from high impedancesources, and since the elements have considerable capacity, it isdifilcult to apply square wave voltages to them.

In accordance with this invention. these diiilculties are avoided byutilizing magnetic fields rather than electric fields to cause theelectron beam to impinge accurately upon the desired color element. Itis well known that an electron proceeding in the same general directionas a magnetic field will tend to follow the course of the magnetic fiuxlines; and further, that an electron crossing a magnetic fiux line willbe deflected in a direction normal both to its original direction ofmotion and the direction of the flux line. In accordance with myinvention, magnetic flux lines are made to pass through or near thedesired screen element in such a manner that electrons emanating fromthe cathode and directed in the general direction 01' the desired screenelement will be deflected to that screen element.

3 In one form of my invention. I accomplish this result by passingcurrent through the wires comprising the screen elements and by properlyFigure 1'! shows a general view of the alternate embodimentof myinvention as shown in Figures changing the current passing through theelements to cause the electron beam to be urged successively towardelements havingthe color response desired. In another form of myinvention, I provide a combination of diamagnetic and paramagneticmaterials and-produce the necessary flux lines by alternate excitationof longitudinal and transverse magnetic fields. In a third form of myinvention, a transverse magnetic field is utilized in conjunction withcolor phosphors located in protected spaces of a single set of screenelements.

The primary object of this invention is to provide a method of and ameans for reproduction of television images in color.

Another object of this invention i to provide a method of and a meansfor reproduction of television images in perspective.

A further object of this invention is to provide more accurate scanningof an electron beam.

Also in accordance with my invention more accurate scanning of anelectron beam is accomplished without high potentials by the use ofmagnetic fields. I

In accordance with other aspects of my invention, more accurate scanningof an electron beam is accomplished by the use of interspersedparamagnetic and diamagnetic screen particles, together with transverseand longitudinal magnetic fields.

In accordance with a further aspect of my invention, more accuratescanning of an electron beam is achieved by a screen composed ofoppositely spaced protected luminescent surfaces, together with amagnetic field.

Other objects and aspects of thi invention will be apparent from thefollowing specifications and claims.

In the drawings: Figure l is a general view of the preferred form of myinvention showing the cathode ray tube and screen elements.

- Figure 2 is an expanded plan view of the screen of the tube shown inFigure 1 showing the disposition of image elements.

15 and 16.

Figure 18 shows a greatly magnified view of a third form of myinvention.

Figure 19 shows in perspective my invention illustrated in Figure 18.

.Figure 20 shows a greatly magnified view an additional form of myinvention.

Referring in more detail to Figure 1, a cathode ray tube l, containingelectron beam producing means 2 and electrostatic deflection plates 4 isprovided with screen 3 composed of three separate groups of parallelelements 5, 6, and I. Electron producing means 2 generates an electronbeam il adapted to strike image screen 3 and to be deflected across itsarea in synchronism with the transmission system by the electrostaticfield between deflection plates 4.

The structure of image screen 3 may be better understood by reference toFigure 2. As shown in'Figure 2, the image screen comprises threeseparate groups of parallel screen elements. 5. I and I. These threegroups are assembled alternately so that any adjacent three elements,ll, comprise screen elements of the three separate color groups. Onegroup, say 5, is provided with a luminescent material or filter of greencolor. A second group, say 6, is provided with a luminescent material orfilter of red color. A third group, say I, is provided with aluminescent material or filter of blue color. Hence, scanning of eachgroup of three adiacent elements. ll produces an image containing all ofthe three primary colors. This image will appear as natural colorbecause of the persistence of vision and the inability of the human eyeto distinguish separate screen elements in image element group II.

Figure'3 shows 'a'long'itudinal cross section of my tube as shown inFigure 2. In Figure 3, the electron beam ii is caused to impinge uponsurface of a group such as In by electrostatic defiection plate l2. Thiscan be accomplished without great precision in the electric fieldbetween the defiection plates and a conventional electrostatic scanningsystem may be employed.

-' It is, however, not possible to cause the electron Figure 3 is alongitudinal section of the tube of Figure 2 showing the limit ofcontrol of the electron beam by conventional scanning methods.

' tions of current flow in the elements of the screen of the tube ofFigure 2.

Figure 9 shows the current variation with time in the screen elements ofthe tube of Figure 2.

Figures 10, 11 and 12 show the connection of image elements to a commoncurrent source required to achieve the current flow shown in Figures 6,7, 8 and 9.

Figure 13 shows a commutator adapted to achieve the current flow shownin Figures 10, 1 and 12.

Figure 14 shows in block form a complete television receiving systemembodying my invention as shown in Figure 1. I

Figures 1541 and 15b are greatly magnified longitudinal and transverseviews of an alternate embodiment of my invention utilizing paramagneticand diamagnet screen elements.

Figure 16 is a magnified cross section through coil 5|.

cathode ray tube to provide a means of causing the electron beam toimpinge on a predetermined screen element 5, 8 or I of image elementgroup I0.

The wires comprising screen 3 of cathode ray tube i are ofelectro-conductive material adapted to carry an electric current. Asshown in Figure 1, I provide for current flow in each separate group ofelements independently of current fiow in the other elements. In orderto cause the electron to impinge upon a particular The combination orcurrent flow in elements I and 1 causes a magnetic field to be set upproducing flux lines substantially as shown at l2. These flux lines areconcentrated between elements I and 1 and pass through elements 6, andthe resultant field urges the electron beam toward the elements 6. Inorder to achieve maximum concentration of flux lines and a maximumdegree of effectiveness from the separate elements 5, 6 and 1, I use amaterial having a magnetic permeability of high value in the screenelements. Any ferromagnetic material such as iron, nickel, cobalt, etc.,can be used for this purpose. Soft iron wire is particularly suitable asit may have a permeability of 1,000 or more.

Figure 5 shows in greater detail a typical construction of the separateelements of my image screen. Each element consists of a thin wire l3 ofsize sumcient to carry the current necessary the electron beam toimpinge upon the desired element. Preferably this wire is of materialhaving high permeability. If greater current is required than can beachieved by round wire, an oval or rectangular shape may be used; thelong axis of the wire being parallel with the direction of the electronbeam. Each wire 13 is covered with a material which emits desired colorwhen excited by an electron beam. In the case of elements 5, the coatingI4 is of a material producing a red color. In the case of elements 8,the coating l5 emits a blue color. Finally in the case of elements 1,the coating l6 produces a green color. Alternatively, the fluorescentcoatings I 4, l5 and It may produce white light and filter coatingsadded to each element to give the desired color.

In addition to the conducting element l3 and the luminescent elementsll, l5 and It on the screen elements 5, 6 and 1, an insulating layer 32is provided. This layer is located between each conducting element l3and its luminescent surface, l4, l5 or Ii. This insulation preventschemical spoiling of the luminescent surface by the conducting elementl3 and also acts as an electrical insulator, thereby increasing the lifeof the screen and preventing current flow between the conductingelements l3.

Figures 6, '7 and 8 are enlarged views showing current flow in theseparate groups of elements as the electron beam is caused to impingeupon elements 5, 1 and 6 respectively. In Figure 6. it is desired tocause the electron beam to impinge upon elements 5. This is accomplishedby causing current flow in one direction in elements 6 and in theopposite direction inclements 1. Although I have shown current flowtoward the observer in elements 1 and away from the observer in elements6, it will be recognized that the opposite current flow will produce thesame magnetic effects in so far as deflection oi the electron beamtoward elements 5 is concerned. In Figure 7. I have shown the currentflow required to cause the electron beam to impinge upon elements I. Inthis case. current flow may be away from the observer in elements 5 andtoward the observer in elements 3, or vice versa. In Figure 8, I haveshown the current flow required to cause electron beam to impinge uponelements 6. Current flow toward the observer in elements 5 and away fromthe observer in elements 1, or the reverse, is required to achieve thedesired result.

Since the electron stream is caused to impinge successively on elements3, '1 and 8, the

current flow in the various elements must be changed in accordance withtime in the sequence of Figures 6, 7 and 8. Figure 9 shows one ar-zapplying a direct voltage to combinations of elements 6, 1 and 5. Thisis shown in detail in Figures 10, 11 and 12, Figure 10 corresponding toFigure 6, Figure 11 corresponding to Figure 7, and Figure 12corresponding to Figure 8. In Figure 10, direct voltage I is connectedin series with IS and M which represent elements 3 and 1 respectively.The connection of terminals l1, I3, is and 20 of i3 and I4 is arrangedso that current flow in I3 is in the opposite direction to current flowin H. This current flow is shown in more detail for particular elementsof groups l3 and It by arrows 51 and 58 of Figure 1. In Figure 11,direct voltage I6 is connected to cause current flow in elements l3 andIf: in opposite direction whereas in Figure 12 current flow is inelements I and IS in opposite direction. As dis-' cussed above, the sameresult would be obtained if the reverse current flow is used in bothelements, that is, the polarity of direct current source l6 may bereversed without altering the operation of the system.

Figure 13 shows a mechanical commutator system whereby the connectionsrequired in Figures 10, 11 and 12 may be automatically obtained. Twocommutators 31 and 33 are provided with 6 commutator segments each. Thesegments on commutator 31 are 26; 21, 23,29, 30 and 3|, whereas thesegments on commutator 33 are 3|. 3 35 and 36. Brushes 24 and 25 rideonopposite ends of commutator 31, while brushes 2! and 30 ride on oppositeends of commutator 33. The two commutators are mechanically connectedand rotate in synchronism at a velocity determined by the rate at whichit is desired to transfer between the three separate groups of colorelements. The purpose of commutator 31 is to supply voltage from directcurrent source |3 to the desired combination of elements H, II and I5.In order to achieve this result, I connect commutator segments 23, 21,23, 23, 33 and 3| to terminals I1, i8, I9, 20, 2| and 22 of elements i3.I4 and IS in accordance with Table 1. As the commutator rotates, thevoltage from I3 is thereby successively applied to the desired group ofelements. The purpose of commutator 33 is to connect elements l3. I3 andI5 together as required for the sequence shown in Figures 10, 11 and 12.In order to do this, I connect commutator segments 3|, 32, 33, 34, 35and 33 to terminals l1, l8, I9. 20, 2| and 22 of elements l3, l4 and I!as shown in Table 2. Since commutator 31 rotates with commutator 33. Ithereby apply voltage IE to the desired terminal and at the same timeconnect the desired terminals so as to achieve the sequence shown inFigures 10, 11 and 12. As the commutator rotates. the current isreversed for the same point at two successive cycles of operation, butthis does not alter the resultant motion of the electron beam.

As an alternative to the above described me chanical commutator system,an electronic method may be used. This system could consist -oftriggered relaxation oscillators arranged to cause current flow in eachscreen element in accordance with the requirements of Figures 6, '1, 8and 9. I

A complete television receiving system showing the application of myinvention is shown in Figure 14. In the system, 43' is an antenna bywhich radio frequency energy containing television intelligence isreceived, and 42 is a radio receiver producing video frequency outputtogether with timing signals. Output of unit 42 is passed to videoamplifier 44 which places upon a control grid in cathode ray tube I asignal proportional to the received signal from the antenna. Also fromunit 42 a circuit goes to the synchronizing and separation unit 4|. Thisunit feeds the raster deflection circuit 51 which applies to elements 4of cathode ray tube suitable deflecting potentials causing cathode raybeam II to impinge upon a particular group I0. Unit 4| also feedscurrent source and commutator 39 which in turn applies current toelements 5. 6 and 1 of screen. thereby causing the electron beam II toimpinge on the desired element of screen 3. Synchronizing pulsesreceived through antenna 43, receiver 42, and separating circuit 4|,cause unit 39 to excite the separate groups of elements 5. 6 and 1 inaccordance with the scanning at the television transmitter, therebycoordinating the 'receiverwith the transmitter and producing a faithfulcolor television image.

Proper choice of the area of the conductors in the screen elements of myinvention as shown in Figure 1 permits operating the luminescentmaterial at a predetermined high temperature. thereby taking advantageof themost favorable operating temperature of the phosphor.

Figures 15, 16 and 17 show an alternate form of my television receivingsystem. In this form, I provide a cathode ray tube screen consisting ofa group of small screen elements of para-magnetic and diamagneticparticles. Each particle is covered witha fluorescent material, thematerial on the paramagnetic particles producing one color and thematerial on the diamagnetic particles producing another color. Toprovide a means of. selectively producing one color, I

provide a transverse magnetic field produced by elements 4! and II and'acoaxial magnetic field produced by coil".

The diamagnetic material composing screen elements 41 has a permeabilityof less than unity. As a result, magnetic fiux tends to avoid theseelements and take other paths having less reluctanee. When thetransverse magnetic field is produced by coil II and magnetic core 40,the

flux distribution through the elements composing the tube screen issubstantially as shown in Figure 150. As shown in the figure, themagnetic flux tends to pass around diamagnetic elements 41 and throughparamagnetic elements 46. Accordingly electrons impinging on the screenin a direction perpendicular to the cross section shown in the figurearedeflected by the strong magnetic field at paramagnetic particles '46since a force acts on these electrons normal to the direction of themagnetic field and to their direction of motion. Hence, when thetransverse magnetic field is used, the color corresponding todiamagnetic elements 41 is produced.

When the coaxial magnetic field is produced by current in coil 5|,magnetic lines of force parallel to the direction of motion of theelectrons pass through elements 46 and 41. Since the paramagneticelements it have a permeability greater than unity, and the diamagneticelements have a permeability less than unity, the flux tends to passthrough elements 48. This causes the electron beam to tend to impinge onparamagnetic elements 46 as shown in Figure 16 and the colorcorresponding to these elements is produced.

In order ,to produce a composite two-color television image, Ialternately excite axial field coil Si and transverse field coil 50 inaccordance with the scanning color desired. I accomplished this by useof a source of commutated electric current 52, Figure 17, triggered bysignals indicating the color being scanned by the televisiontransmitter.

Since the control over the electron beam produced by the magnetic fieldof transverse coil 50 or coaxial coil 5| is restricted to the regionimmediately adjacent to the screen, the two fields are arranged toprovide a narrow fiux distribution.

In the case of the transverse magnetic structure 49, this canbeaccomplished by using a narrow shape as shown in the cross section ofFigure 1511. In the case of the coaxial magnetic field, coil ii is madevery narrow with respect to its diameter, thereby achieving maximumconcentration of the field.

represents a transparent screen adapted to produce a primary color. saygreen. Elements I4 consist of parallel transverse strips having amaterial on the upper surface 56 adapted to produce a second primarycolor, say red, when an electron beam impinges upon this surface. Onlower surface 55 of elements 54, I provide a second coating of materialadapted to produce a third primary color, blue, when electrons impingeupon that surface. Hence, I am enabled to produce the three primarycolors by having the electron beam impinge upon screen 53, upper surface56 of elements 54 and lower surface 55 of elements 54. In order to focuselectron beams II, I provide a transverse magnetic field in the planeand immediate vicinity of the elements 54 and parallel with them. Whenthis field is. in

-the direction into the elements as shown in Figure 18, the cathode raybeam II is deflected upward A third modification of my invention isshown in cross section in Figure 18. In the figure, 53

toward the under surface 55 of elements 54. This is the condition shownin Figure 18. When the field is not excited, the electrons continuethrough the screen formed by elements 54 to screen 53 where the colorcorresponding to the coating on 53 is produced. When the magnetic fieldis in a direction out of the cross-section shownin Figure 18, theelectron beam is deflected downward to upper surface 56 of element 54,thereby producing the third primary color. By providing a selectiveexcitation of the magnetic field in accordance with synchronizing,pulses from the television transmitter, I am enabled to selectivelyproduce the three primary colors in accordance with the scanning of thetelevision transmitter, thereby reproducing a television image in itsnatural color. Figure 19 shows in perspective the disposition of thecathode ray tube I, electron beam l I, screen elements I! and 54 andmagnetic field coils 63 used in my invention as shown in Figure 18.

Figure 20 shows an alternate method by which my invention as shown inFigure 18 may be practiced. In the figure, the cathode ray tube screenconsists of plate 51 having a plurality of parallel grooves 58 andpreferably of high reluctivity material. The upper surface of the groove51 is coated with a luminescent material which produces one primarycolor when struck by an electron beam. The bottom surface of each groove80, is coated with a luminescent material producing a second primarycolor when impinged upon by an electron beam. The lowest surface of eachgroup I is coated with a material producing a third primary color whenstruck by the electron beam. By providing a transverse magnetic fieldsimilar to that used in my invention as shown in Figure 18, I am able toselectively cause electron beam II to impinge upon surfaces 59, 60 andGI. I therefore selectively produce any one color on the cathode raytube screen in accordance with scanning of the television transmitter.

In addition to producing a color television image, my television systemas described herein is capable of use in the transmission ofstereoscopic images by using of one color to show the picture taken fromone stereoscopic camera and another color to show the picture from asecond stereoscopic camera. This method is well known in the art, beingdescribed in more detail in Patent 2,307,188.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the, payment of any royalties thereon or therefor.

My invention as described herein, is capable of wide variation andmodification without departing from the spirit and scope of theinvention as set forth in the appended claims.

I claim as my invention:

1. In a television system including a transmitter and areceiver, acathode ray tube in said receiver having an image modulated electronbeam, means deflecting said beam in accordance with signals from saidtransmitter, a screen comprising electrically parallel screen wireshaving a dimension perpendicular to said electron beam and to theirlength small compared to the size of the image elements on said screenand arranged in a multiplicity of interleaved groups, the elements ofeach group having a common connection at each side of said screen andadapted to produce a primary color when impinged upon by the electronbeam, a magnetic flux producer including said screen wires and causingflux around said wires and causing said beam to selectively impinge uponone of said groups in accordance with the scanning of objectives by saidtransmitter.

2. In a color television receiver, a cathode ray tube, a screen in saidtube comprising parallel conducting elements coated with fluorescentmaterial, said conducting screen elements being divided electricallyinto a plurality of groups, the elements of each group being arranged ininterleaved order, the elements in each group being adapted to produce acommon color different from that of any other group when impinged uponby an electron beam and being connected in parallel in a closedelectrical circuit, and a source of electric current intermittentlyenergizing said circuits in such sequence as to cause the electron beamin said tube to selectively impinge upon said groups in accordance withthe color group desired to be actuated.

3. In a television receiver for receiving television images in naturalcolor, a cathode ray tube, an electron beam in said tube, a screen insaid tube composed of parallel conducting screen elements covered withluminescent material, said conducting elements being electricallyconnected in three groups, the elements of each group being electricallyparallel connected in a closed electrical circuit and interspersed withelements of the other groups and adapted to produce upon excitation bysaid electron beam a particular color, a source of electric currentenergizing said circuits in suchsequence as to produce current flow insaid conducting elements including magnetic flelds of directioneffective to cause said electron beam to selectively impinge upon aparticular group in accordance with the scanning of said televisionsystem.

4. A television system as in claim 1, the screen wires composed offerromagnetic material.

5. A television receiver as in claim 2, the screen elements composed offerromagnetic material.

6. A television receiver as in claim 3, the screen elements composed offerromagnetic material.

7.'In a television system including a transmitter, an image scanner insaid transmitter cyclically responsive to at least three different imagecolors, a cathode ray tube, a screen in said tube composed of parallelconducting elements coated with fluorescent material, said elementsbeing insulated from said fluorescent material and electricallyseparated into interleaved color groups corresponding in number to thecolors scanned by said image scanner, the elements of each of saidgroups being electrically parallel connected in a closed electricalcircuit, a source of commuted electric current so energizing saidcircuits as to cause current flow and consequent beam-deflectingmagnetic fields in opposite directions in the two color groups adjacentto the group corresponding in color to the group being scanned by saidtransmitter.

8. In a television system, a cathode ray tube, an electron beam in saidtube, a screen in said tube comprised of parallel conducting elementsclose to luminescent material, said elements electrically separated intothree color groups and insulated from said material, the elements ofeach mama's 9. In a color television receiver, a cathode ray tube, ascreenin said tube comprised 01 parallel conducting screen elementshaving a non-circucal circuit including said elements connected inparallel with each other to aicurrent source.

' 10. In a cathode ray tube, an electron beam, a;

' 12 around said plate adapted to cause said electron beam toselectively impinge upon said planes. -17. Ina color televisionreceiver, a cathode ray tube, an electron beam, a screen composed of a"transparent plate, a plurality 01' parallel grooves on one side of saidplate and upon which an elecscreen composed of parallel conductingscreen elements coated with a luminescent material, the elements beingconnected in groups in parallel in closed electrical circuits, a sourceoi commuted electric current connected to said circuits in such sequenceas to cause saidelectron beam'to selectively impinge on said elements,

.11. A cathode ray tube screen'comprising interspersed ferromagnetic anddiamagnetic partlclu covered with luminescent material.

12."A cathode ray tube screen comprising a random combination oiparticles or i'erromag netic material coated with-luminescent materialof one color and particles 01' diamagnetic material coated withluminescent material of another color.

13. The method of producing color television images, comprising passinglongitudinal and transverse magnetic fields selectively in accordancewith the instantly televised member of a complementary color pair. on acathode ray tube screen composed of a random combination of particles oiferromagnetic material coated with I upon said plane sides.

tron beam impinges, each oi said grooves havin three plane sides, one ofthe said sides being normal to the electron beam, and the other twosides be Parallel to the electron beam and approximately parallel toeach other, each of said plane sides being coated with a luminescentmaterial producing a difl'erent primary color when struck by an electronbeam, an electro-magnet associated with said stream at the screen andadapted to cause said electron beam to selectively impinge 18. A cathoderay tube,.a screen in said tube comprised of recurrent groups ofelemental areas of luminescent material, each group including areas of aplurality of colors of luminesence, and a magnetic field producer inclose proximity to said screen operative to set up a magnetic fieldaround said elemental areas.

19. A television system as in claim 8, the luminescent material coatedon each screen element.

20. A cathode ray tube as in claim 15 in which the first mentionedscreen is transparent.

21. A cathode ray tube as in claim 16 in which the plate is transparent.

22. In a cathode ray tube, a screen, a plurality of parallel conductingelements substantially in the plane of said screen and divided intogroups ter and a receiver, a cathode ray tube in said receiver, a screenin saidtube comprising a heterogeneous mixture oi! particles ofIerromagnetic material coated with luminescent material oi. one color,and particles of diamagnetic material coated with luminescent materialof a complementary color, means producing a transverse magnetic fieldacross'said screen, means producing a coaxial magnetic field throughsaid screen,

means actuating said magnetic field producing means selectively inaccordance with the scanning of respective color images by saidtransmitter.

15. In a cathode ray tube, an electron beam, a screen adapted to producecolored illumination upon incidence of an electron beam} aplurality ofparallel spaced screen'elements mounted, parallel to said screen andadapted to produce one color when struck from below by an eiectron beamand a second color when struck from above by an beam and two of saidside's approximately in the plane of said beam and parallel to eachother,-

each of said plane sides coated with a luminescent materiahthe coatingoneach of said sides producing a diil'erent primary color when impingedupon by an electron beam anda magnetic field the elements of eachgroupbeing connected in parallel in a closed electrical circuit,luminescent material close to said elements, said luminescent materialhaving a difierent color oi luminescence tor each group and means forintermittently supplying current to each closed circuit.

23. A cathode ray tube as in claim 22, the luminescent materialcomprising a coating on each co'nducting element.

24. A cathode ray tube as in claim 22, the luminescent materialcomprising a coating on each conducting element and separated therefromby an insulating material.

25. The method 01 producing a color television picture wherein anelectron beam is directed to one of a group oi electrically parallelinterleaved conducting elements characterized by the step -01 causingcurrent flow in one direction in the elements on one side of said groupand current flow in the opposite direction in the elements on the otherside of said group.

26. In a television system, a receiver, a cathode ray tube in saidreceiver having an image modulated electron beam. means deflecting saidbeam in accordance with signals from said transmitter, a screencomprised of a multiplicity of screen wires arranged in threeinterleaved groups, the elements of each group electrically parallelconnected in a closed circuit, means under control of the transmitterfor supplying current to each closed circuit in such sequence as toproduce magnetic flux around said wires in said groups in accordancewith the scanning of an objective by said transmitter.

27. In a television system, a receiver, a cathode ray tube in saidreceiver having an image modulated electron beam, means deflecting saidbeam in accordance with signals from said transmitter, a screencomprised of parallel wires having a dimension perpendicular to saidelectron beam comparable in size to image elements on said 13 screen andarranged in a multiplicity of interleaved groups, the wires in eachgroup being connected in parallel in a closed electrical circuit,

means under control of the transmitter for supplying current to eachclosed circuit in such sequence as to produce magnetic flux around thewires in said groups causing said beam to selectively impinge on saidgroups in accordance with scanning of objectives by said transmitter.

28. In a television system, a receiver, a cathode ray tube in saidreceiver having an image modulated electron beam, means deflecting saidbeam in accordance with signals from said transmitter, a screencomprised of parallel screen wires arranged in a multiplicity ofinterleaved groups, the elements of each group being connected inparallel in a closed electrical circuit and adapted to'produce a commoncolor when impinged upon by an electron beam, means intermittentlysupplying current to each closed circuit in such sequence as to producemagnetic flux around said wires causing said beam to selectively impingeon said groups in accordance with the scanning of objectives by saidtransmitter.

29. In a color television receiver, a cathode ray tube, a screeen insaid tube comprising parallel conducting elements coated withfluorescent material, said conducting screen elements being divided intoa plurality of groups, the elements of each group being electricallyconnected in parallel in a closed electrical circuit and arranged ininterleaved order, a source of electric current supplying current toeach closed circuit in such se- 30. In a television system including atransmitter, an image scanner in said transmitter cyclically responsiveto image colors, a cathode ray tube, a screen in said tube composed ofparallel conducting elements coated with fluorescent material, saidelements being electrically separated into interleaved color groupscorresponding in number to the colors scanned by said image scanner, theelements of each of said groups being electrically parallel connected ina closed electrical circuit including a source of commuted electriccurrent, said source disposed to cause current flow in oppositedirections in the two color groups adjacent to the group correspondingin color to the group being scanned by said transmitter.

31. In a cathode ray tube, a screen composed of a. plate, a plurality ofgrooves on one side of said plate and upon which an electron beamimpinges. each of said grooves having three plane sides, one of the saidsides normal to the electron beam and two or said sides approximately inthe plane of said beam and parallel to each other, each of said planesides coated with a luminescent material, the coating on each of saidsidesproducing a different color when impinged upon by an electron beamand magnetic means for causing the beam to selectively impinge on theplane sides of the grooves for selective color production thereon.

32. In a television system including a transmitter and a receiver, acathode ray tube in said receiver having an image modulated electronbeam, means deflecting said beam in accordance with signals from saidtransmitter, a substantially planular screen comprised of a multiplicityof uniformly interspersed groups of elements, each group of elementshaving characteristics which differ from any other group when saidelectron beam impinges thereon, at least one closed electrical circuitfor producing resultant magnetic fields in the plane of said screenwhich direct said electron beam during deflection thereof to impingeupon said groups of elements in sequence, and means under control of thetransmitter for supplying current to said circuit.

33. In a television system including a transmit- 1 ter and a receiver, acathode ray tube in said receiver having an image modulated electronbeam, means deflecting said beam in accordance with signals from saidtransmitter, a screen comprised of a multiplicity of elements arrangedin a plurality of uniformly interspersed groups, means characterized bya negligible electric potential causing a varying magnetic field aboutsaid screen elements, said magnetic field being arranged to cause saidelectron beam to impinge selectively upon each of said groups inaccordance with the scanning of an objective by said transmitter.

THORJNTON W. CHEW.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES- PATENTS Number Name Date 2,280,946 Goldsmith Apr. 28,1942 2,294,820 Wilson Sept. 1, 1942 2,307,188 Bedford Jan. 5, 19432,312,792 Baeuford Mar. 2, 1943 2,416,056 Kallmann Feb. 18, 19472,446,249 Schroeder Aug. 3, 1948 2,446,440 Swedlund Aug. 3, 19482,461,515 Bronwell Feb. 15, 1949 FOREIGN PATENTS Number Country Date443,896 Great Britain Mar. 10, 1936

